Showing papers by "University of Fribourg published in 1986"
133 citations
TL;DR: It is concluded that the ON‐center and OFF‐center afferent pathways that are organized at the retinal level remain generally segregated in the tree shrew through the first synapse in the striate cortex.
Abstract: The organization of ON and OFF responses and ocular dominance in the striate cortex of the tree shrew was electrophysiologically investigated by using flashed, stationary visual stimuli presented monocularly to either the ipsilateral or contralateral eye. We measured cortical multi-unit activity at 25-micron intervals with glass-insulated platinum-plated tungsten microelectrodes. Penetrations were made perpendicular to the cortical layers and the responses were quantitatively analyzed in layers IIIc to V. In sublayers IIIb, IIIc, and upper V, phasic responses of approximately equal magnitude occurred to both light ON and light OFF (ON-OFF regions). In layer IV, tonic as well as phasic responses were often evoked by the flashed spot of light. In sublayer IVa stronger responses occurred to light ON than to light OFF (ON region) while in sublayer IVb stronger responses occurred to light OFF than to light ON (OFF region). In an ON region, the increased neural activity that occurred at light ON was often accompanied by a decrease in activity below baseline level at light OFF. A similar decrease often occurred in an OFF region at light ON. Recordings from the region of the cell-sparse cleft in layer IV were characterized by ON-OFF responses, signalling a transition zone between sublayers IVa and IVb. In addition, the responses to stimulation of the ipsilateral eye typically were very weak in the cleft region. In the other regions examined, the multi-unit activity generally was driven binocularly with slightly greater responses being elicited by the contralateral eye. We conclude that the ON-center and OFF-center afferent pathways that are organized at the retinal level remain generally segregated in the tree shrew through the first synapse in the striate cortex. In addition, our recordings confirm that a horizontal organization of ocular dominance occurs in layer IV of the striate cortex in tree shrews.
47 citations
TL;DR: The cross sections for the production of charged pions and protons from the annihilation of 608-MeV/c antiprotons on C, Y and U are presented and are seen to be in good agreement with intranuclear-cascade calculations.
Abstract: The cross sections for the production of charged pions and protons from the annihilation of 608-MeV/c antiprotons on $^{12}\mathrm{C}$, $^{89}\mathrm{Y}$, and $^{238}\mathrm{U}$ are presented. The sources of pion and proton emission are inferred from the rapidity distributions of the data. The results are compared to and seen to be in good agreement with intranuclear-cascade calculations.
40 citations
TL;DR: In this article, an improved muonic-atom experiment was performed to search for long-range muon-hadron interactions, where the authors measured the wavelengths of the 3 d 5 2 −2 p 3 2 X-ray transitions in 24Mg and 28Si with the bent-crystal spectrometer at the SIN muon channel.
38 citations
TL;DR: In this paper, the 1H-NMR data were used to characterize the 2-phenylpyridine-platinum(II) and cis-bis-thienyl pyridine (2-THN) complexes.
Abstract: Cyclometallated complexes of the type cis-bis(2-phenylpyridine)platinum(II) (C22H16N2Pt) and cis-bis(2-(2′-thienyl)pyridine)platinum(II) (C18H12N2S2Pt) undergo thermal or photochemical oxidative addition (TOA or POA) reactions with a number of substrates. TOA (with CH3I, CH3CH2I etc.) yield mixtures of several isomers which rearrange slowly (within ca. one week at room temperature) to one of the possible cis-isomers. CH2Cl2, CHCl3, or (E)ClCHCHCl, e.g., do not react thermally. POA yield directly complexes of Pt(IV) with the halide and a σ-bonded C-atom in cis-position. The configuration, as assigned by extensive use of 1H-NMR data, can be characterized for the two chelating ligands C … N and C′ … N′ by C,C′-cis; N,N′-cis and C(chelate), Cl-trans.
38 citations
TL;DR: The results suggest that the selective target-directed neurotoxic action of MPTP on dopamine neurons in monkeys is mediated via the dopamine uptake mechanism and treatment with the catecholamine uptake blocker nomifensine counteracted the behavioral, histological and neurochemical effects induced by MPTP.
Abstract: Administration of MPTP (1-methyl-1,2,3,6-tetrahydropyridine) to Macaca fascicularis monkeys produced severe parkinsonism (hypokinesia, tremor, rigidity, aphagia, adipsia) and more than 90% loss of nigral dopamine neurons, striatal dopamine content and striatal 3H-mazindol binding. Treatment with the catecholamine uptake blocker nomifensine counteracted the behavioral, histological and neurochemical effects induced by MPTP. For obtaining best protection, nomifensine had to be administered for weeks after MPTP. The results suggest that the selective target-directed neurotoxic action of MPTP on dopamine neurons in monkeys is mediated via the dopamine uptake mechanism.
35 citations
TL;DR: The results indicate that the SMA has oligo- or possibly even monosynaptic connections with motoneurones, but that these connections are less dense than those from MI.
Abstract: Intracortical microstimulation of the supplementary motor area (SMA) was studied in awake monkeys. With short trains of micropulses, contralateral muscle twitches mainly in shoulder and proximal arm muscles were elicited. There was an indication of a rostro-caudal representation of distal to proximal forelimb, trunk, and proximal to distal hindlimb muscles. However, an intermingling of efferent zones was much more prominent as compared to the precentral motor cortex (MI). All efferent zones to the spinal cord were clustered in the caudal half of the SMA, and we failed to detect face and ocular movements (except at one stimulation site) when microstimulating the rostral portions of the SMA. Single micropulses were also injected in efferent zones of the microexcitable cortex in order to investigate post-pulse facilitation of sustained EMG activity. For motor cortex (MI) stimulation, post-pulse facilitation was prominent and observed in 14 of 17 tested stimulation sites. The incidence of facilitation in comparable muscles obtained with SMA stimulation was only 20 out 54 tests. The onset latencies of EMG modulation obtained from the two areas were in the same range but the amount of modulation in the SMA was less conspicuous than in MI. These results indicate that the SMA has oligo- or possibly even monosynaptic connections with motoneurones, but that these connections are less dense than those from MI.
33 citations
TL;DR: The synthesis of a mononuclear Rh(III) complex, as a representative example of a series of related species, containing two cyclometallating ligands ppy (2-phenylpyridine) and one diimine bpy(2,2′-bipyridine), from a binuclear Cl-bridged compound is described in this article.
Abstract: The synthesis of a mononuclear Rh(III) complex, as a representative example of a series of related species, containing two cyclometallating ligands ppy (2-phenylpyridine) and one diimine bpy (2,2′-bipyridine) from a binuclear Cl-bridged compound is described. The absorption spectrum shows a maximum at 364 nm (e = 7000), with a very weak shoulder (e = 10) at 454 nm. This band is tentatively assigned to a metal-to-ligand charge-transfer transition. A reversible, one-electron reduction appears in the cyclic voltammogram at E1/2 = −1.41 V (vs. NHE) and a irreversible oxydation at Ep = + 1.1 V. A detailed NMR analysis including 13C-NMR, NOE, SFORD as well as deuteration of the bpy ligand indicates the formation of only one isomer, having a C2 axis, bisecting the bpy ligand, with the two carbon ligands in cis-position. 103Rh, 13C and 103Rh,H couplings are observed.
32 citations
01 Sep 1986
TL;DR: An efficient method to compute mean passage times and absorption probabilities in Markov and Semi-Markov models using the state reduction approach introduced by Winfried Grassmann for the computation of the stationary distribution of a Markov model is discussed.
Abstract: This paper discusses an efficient method to compute mean passage times and absorption probabilities in Markov and Semi-Markov models. It uses the state reduction approach introduced by Winfried Grassmann for the computation of the stationary distribution of a Markov model. The method is numerically stable and has a simple probabilistic interpretation. It is especially stressed, that the natural frame for the state reduction method is rather Semi-Markov theory than Markov theory.
25 citations
TL;DR: It is suggested that the SMA exerts subtle inhibitory effects on the motor cortex or its inputs through its influence on area 4 neurones to kinesthetic stimuli.
25 citations
TL;DR: This article showed that perylene undergoes three distinct electron-transfer reactions in MeCN at 20°, and these processes originate probably from the thermally relaxed excited states of perylene.
Abstract: Laser-flash-photolysis experiments show that, in MeCN at 20°, perylene (P) undergoes three distinct electron-transfer reactions: These processes originate probably from the thermally relaxed excited states of P.
TL;DR: In this paper, the dual luminescence of 4-N,N-dimethylaminobenzonitrile (DMABN) has been observed in 1-fluoropentane; only the normal emission is observed in hexane and in perfluorohexane.
TL;DR: In this paper, the problem of how to choose the collocation points so that both u and u converges in the space of continuous polynomial splines of degree m ⩾ 1 with collocation occuring at the Gauss-Legendre points was studied.
TL;DR: In this paper, the symmetry and spin-orbit splitting of the emitting states of a single-crystal cis-bis(2-phenylpyridine)platinum (II) were determined.
TL;DR: In this article, the average population of the electronic K-shell during the pionic transition has been determined from the line shape of pionic X-ray peak which allows a precise calculation of the electron screening correction to the transition energy.
TL;DR: The pontocerebellar pathway in the brachium pontis, is known to convey signals from various cortical and subcortical visual structures to the cerebellum, and the effects of motor dysfunction of cerebellar origin are compared.
TL;DR: Using an improved technique of “surface transplantation,” supernumerary appendages of any desired type in a particular abdominal position are generated and indicate that sensory axons of homologous appendages on the one hand, and their central targets on the other, share serially repeated surface markers.
TL;DR: In this paper, a complete scheme of OT+ rotamers and their connections via single bond-rotation processes is discussed, and the extent of this site dependence varies greatly between different rotammers and between different electronic transitions of a given rotamer.
Abstract: Upon ionization by x irradiation, all‐trans 1,3,5,7‐octatetraene (OT) gives an electronic absorption (EA) spectrum which indicates the formation of at least five different (peri)planar conformations (‘‘rotamers’’) of OT+ next to the parent cation. Some of these undergo specific photochemical interconversions which are discussed on the basis of a complete scheme of OT+ rotamers and their connections via single bond‐rotation processes. None of these photoreactions lead to any other than the initially observed six species which seem to form a distinguished set within the 20 possible OT+ rotamers. By very narrow bandwidth irradiation, interconversions can be induced to take place in a site‐selective fashion. The resulting well‐resolved difference spectra allow an analysis of the site dependence of the different ion’s first two EA bands. Surprisingly, the extent of this site dependence varies greatly between different OT+ rotamers and between different electronic transitions of a given rotamer. Finally, a ...
TL;DR: These maps provide useful guides for neurological diagnosis and neurosurgery, as well as for experimental work on animals, however, it must be realized that the maps are oversimplifications of the complexity seen even in the classical surface stimulation studies.
TL;DR: In this paper, the probability of the radiationless muonic 3d→1s transition in 237 Np, (9±4)%, was obtained by comparing the relative intensities of the main muonic X-ray transitions in singles and coincidence spectra.
TL;DR: It is concluded that locally applied Hex-Cer exerted an accelerating effect on wound-healing angiogenesis.
01 Jan 1986
TL;DR: In this paper, a method for the calculation of the multiplet ligand-field states of transition metal complexes is presented, which involves the use of MS-Xα wave functions, in connection with irreducible tensor operators.
Abstract: A method is outlined for the calculation of the multiplet ligand-field states of transition metal complexes. The procedure involves the use of MS-Xα wave functions, in connection with irreducible tensor operators, and allows the calculation of the elements of the many-electron CI matrices. Comparison of the calculated and experimental multiplet state energies of CrF, CrCl, and MnF allows one to conclude that the method is useful for the prediction of ligand-field spectra of transition-metal complexes.
TL;DR: Aromatic oxanilides, used as polymer light stabilizers, show a remarkably low photo-reactivity both in oxygen-free and in air-saturated solutions.
TL;DR: The induction of cellobiose dehydrogenase shows a dependence on pH andCellobiose concentration which is different to that for endo-cellulase, and the natural inducer of these enzymes and the role ofcellobiose dehydration remain to be elucidated.
Abstract: The cellulolytic fungus Sporotrichum (Chrysosporium) thermophile produces an extracellular cellobiose dehydrogenase during batch culture on cellulose or cellobiose. In chemostat culture at pH 5.6 on cellobiose this enzyme was produced in parallel with endo-cellulase. At pH 5.0 in continuous or fed-batch culture such a pattern was not evident. At constant growth rate in a chemostat with varying pH, activity of these enzymes was found to be poorly correlated. Thus the induction of cellobiose dehydrogenase shows a dependence on pH and cellobiose concentration which is different to that for endo-cellulase. The natural inducer of these enzymes and the role of cellobiose dehydrogenase remain to be elucidated.
31 Mar 1986
TL;DR: In this article, the authors discuss the role of private individuals in the Sozialgeographie, i. e.g., in the Verhalten dem Raume gegenuber verborgene gesellschaftliche Versinnbildlichung.
Abstract: . Das Thema des Privateigentums ist fur das Verstandnis raumlicher Praktiken von grundlegender Bedeutung. Speziell in der Sozialgeographie ist das individualistische Paradigma untrennbar mit jeglichem Theorisationsversuch verbunden. Die Rolle des Privateigentums darf daher nicht bloss unter dem strukturellen Aspekt (z. B. der Verteilung des Grundbesitzes) betrachtet werden, sondern muss auch als eine im Verhalten dem Raume gegenuber verborgene gesellschaftliche Versinnbildlichung angesehen werden. Zur Hervorhebung der Dynamik benutzt der Verfasser einen geo-historischen Ansatz. Er legt zunachst die raumlichen Auswirkungen des individualistischen Paradigmas dar. Danach werden die dem Privateigentum im Rahmen der Verstadterungs- und Raumplanungspolitik auferlegten Beschrankungen abgehandelt. Daraus wird ersichtlich, dass diese fur die Grundeigentumer restriktive Politik nichts anderes ist als eine «soziale Technologie», welche die gesamte Gesellschaft pragt. Jegliche (aktive) Raumordnung hat ihren Ursprung in der gesellschaftlichen Versinnbildlichung des Eigentums und setzt ein Gleichgewicht zwischen privaten und allgemeinen Interessen voraus. Die Untersuchung der Besitzverhaltnisse und deren raum-zeitliche Konfiguration kann daher zu einem neuartigen Verstandnis der Sozialstruktur beitragen.
TL;DR: The aim of the present paper is to present a logical analysis of the free society using the symbolism of the Principia Mathematica, with a few extra-logical symbols being explained when intro duced.
Abstract: The aim of the present paper is to present a logical analysis of the con cept of the free society. The symbolism used will be that of the Principia Mathematica?a few extra-logical symbols being explained when intro duced. Regarding logical symbolism, it must be stressed, that the use of ar tificial symbols is not to be understood as a formalization. For formaliza tion is a procedure by which one abstracts from the meaning of terms and operates on the shapes of the (material) symbols alone?which will not be done here. The symbolism is rather used as a useful shorthand, without which it would be difficult to obtain statements of the desired precision.
TL;DR: The rate constant for dissociation of [Ca(AA − )] +, where (AA − ) is the radical anion of ascorbic acid, has been measured by observation of specific line broadening in the ESR spectrum as discussed by the authors.